Method and apparatus for substrate imaging

ABSTRACT

The invention provides a substrate surface imaging method and apparatus that compensates for non-linear movement of the substrate surface during an imaging sequence. In one aspect of the invention, the imaging method and apparatus compensate for the non-linear substrate surface movement by adjusting the image receiver trigger points to correspond to image positions on the substrate surface. In another aspect, the invention provides synchronous imaging where the distance between each image position is determined by counting the number of stepper motor steps between image positions. In still another aspect, the invention provides for asynchronous substrate imaging by determining an image trigger time between each image position and using the image trigger time to trigger the receiver at the appropriate time to accurately image the substrate surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.09/886,307, filed Jun. 19, 2001 (Attorney Docket No. APPM/5090), whichis incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the invention generally relate to a method and apparatus forsubstrate process inspection and monitoring.

2. Background of the Related Art

A chip manufacturing facility is composed of a broad spectrum oftechnologies. Cassettes containing semiconductor substrates are routedto various stations in the facility where they are either processed orinspected. Semiconductor processing generally involves the deposition ofmaterial onto and removal (“etching”) of material from substrates.Typical processes include chemical vapor deposition (CVD), physicalvapor deposition (PVD), electroplating, chemical mechanicalplanorization (CMP), etching and others. During the processing andhandling of substrates, the substrates undergo various structural andchemical changes. Illustrative changes include the thickness of layersdisposed on the substrate, the material of layers formed on thesubstrate, surface morphology, changes in the device patterns, etc.These changes must be inspected and controlled in order to produce thedesired electrical characteristics of the devices formed on thesubstrate. In the case of etching, for example, end-point detectionmethods are used to determine when the requisite amount of material hasbeen removed from the substrate. More generally, successful processingrequires ensuring the correct process recipe, controlling processdeviations (e.g., gas flow, temperature, pressure, electromagneticenergy, duration, etc) and the like.

To process substrates effectively, the processing environment must besufficiently stable and free from contamination. Sources ofcontamination include wear from mechanical motion, degradation of seals,contaminated gases, contaminated substrates, flaking of deposits fromprocessing chamber components, nucleation of reactive gases,condensation during chamber pumpdown, arcing in plasma chambers and soforth. Such sources of contamination may produce particles that cancontact the substrates and result in defective devices. As thegeometries of device features shrink, the impact of contaminationincreases. Thus, current semiconductor manufacturing sequences routinelyinclude inspection of substrates for particles and/or aberrations toidentify “dirty” processes or equipment.

Currently, comprehensive testing and analysis of substrates for processintegrity and contamination requires the periodic or often constantremoval of one or more substrates from the processing environment into atesting environment. Thus, production flow is effectively disruptedduring the transfer and inspection of the substrates. Consequently,conventional metrology inspection methods can drastically increaseoverhead time associated with chip manufacturing. Further, because suchan inspection method is conducive only to periodic sampling due to thenegative impact on throughput, some contaminated substrates may beprocessed without inspection resulting in fabrication of defectivedevices. Problems are compounded in cases where the substrates arere-distributed from a given batch making it difficult to trace back tothe contaminating source.

Another disadvantage with conventional inspection systems is theprohibitive cost of the systems. Current systems are typicallyexpensive, stand-alone platforms that occupy clean-room space. Due tothe large area, or “footprint”, required by the stand-alone inspectionplatforms, the cost of owning and operating such systems is high. Withregard to particle detection, the cost is further increased because ofthe electro-optics equipment utilized. This equipment is configured toproduce high-resolution detection of small-scale particles and requireshigh-fidelity mechanisms, which are generally expensive to operate.Additionally, considerations of reduced throughput described abovefurther increase the cost of conventional inspection systems.

One method to alleviate the throughput problems of conventionalinspection systems is through in situ inspection. In situ inspection isoften accomplished through the placement of inspection systems along thetransfer paths of the substrates. In situ inspection acquires real-timedata “on-the-fly” about the process and/or the substrates, while thesubstrates are moving between processes, thereby minimizing oreliminating the impact of the inspection on the process throughput. Theinspection systems typically include receiving devices that gathersample images of the moving substrates that are sent to a dataprocessing system for analysis. The image-gathering devices may betime-domain integration cameras (TDI), line cameras, charge coupleddevice cameras (CCD), and the like. An example of an exemplary in situinspection system is described in U.S. patent application Ser. No.09/680,226, entitled “Method and Apparatus For Enhanced EmbeddedSubstrate Inspection Through Process Data Collection And SubstrateImaging Techniques,” filed on Oct. 6, 2000, and which is herebyincorporated herein by reference in its entirety.

Generally, in situ inspection systems require linear and/or synchronizedlinear substrate movements to accurately image a particular positioncoordinate, e.g., a location, on the moving substrate in order to detectand display on a monitoring system defects such as micron sizeparticles, substrate surface conditions or aberrations, and the like.Although movements of the substrate transport system such as frog-legand polar robots, conveyor belts, and other parts of the process systemmay include linear motion during substrate handling, many of the motionsused to handle the substrate transportation are non-linear such as theacceleration and deceleration of the substrates as they are moved intoand out of process chambers. Moreover, as the substrate is being movedfrom one process to the next, the linearity (e.g., smoothness) of thesubstrate motion is further influenced by system issues such as inertia,vibration, friction, and the like. Accordingly, depending upon thedesign and weight of the robot and substrate supporting surfaces, thenumber of available linear substrate movements required by theinspection process may be limited to specific portions of the substratetravel. For example, a frog-leg type of robot typically has two arms,each arm having a jointed arm section that is configured to allow therobot to extend and retract each arm when moving substrates into andfrom process chambers. The robot arms are typically driven by at leastone motor such as a linear motor or stepper motor. During the extensionor retraction of the substrate, the motor is accelerated or deceleratedto extend the substrate or remove the substrate from a chamber or move asubstrate along a transfer path. Typically, the motor has non-linearacceleration and deceleration movements as the motor is started andstopped. Furthermore, the robot arms are typically connected in such away that the retraction and extension motion are usually non-linear witheach rotational movement of the motor. Further, the robot generallyincludes a heavy blade on the extending end of the arms thereforeincreasing system inertia and vibration. Therefore, each rotation of themotor results in non-linear substrate movements through acceleration,deceleration, vibration, and fluctuations in velocity, which can affectthe inspection process.

To resolve the issue of non-liner substrate movement during an in situinspection process, carefully controlled synchronized imaging is oftenused to keep the inspection system synchronized with the substrate.Imaging synchronization generally refers to synchronizing the motion ofthe substrate with the imaging device, such as a line camera, so thatthe images are accurately acquired. For example, a conveyor belt systemmay include small imaging triggers, such as small optical trigger holesformed in the conveyor belt, magnetic devices, and other imagingtriggers physically positioned to trigger the inspection system when itis time to acquire an image. Unfortunately, the imaging triggers aregenerally not physically small enough to allow for high-resolutionimaging of the substrate and, under non-linear motion conditions betweenthe trigger points may result in imaging distortions. Furthermore, dueto the time delay (i.e., response bandwidth) between the imaging triggerand the actual image capture, the imaging trigger often limits theimaging system response. Therefore, to capture images accurately thesubstrate velocity is often slowed by the process system to accommodatethe imaging system, degrading substrate-processing throughput.

Generally, the inspection system to properly acquire an image mustgenerate and/or gather a considerable amount of light in order to focusand detect a defect or particle on the substrate surface as thesubstrate is moved through the process. Typically, the opticalinspection system exposure is established by adjusting camera settingssuch as the aperture, exposure time, shutter speed, frame-rate, and thelike, possibly impairing the image exposure and acquisition accuracy.For example, decreasing the shutter speed to obtain further exposure ofa rapidly moving substrate surface area may blur the image, overexposethe slower moving portions of the substrate, and underexpose the morerapidly moving portions of the substrate. Unfortunately, improving theoptical system response and sensitivity often requires increasing thecost of the equipment typically by adding more light sources, increasingthe output intensity of the light sources, increasing the sensitivity ofthe receiving equipment, and the like. Therefore, improving systemsensitivity often requires slowing the process, thereby decreasingthroughput and increasing the cost of production.

FIGS. 1A-1I illustrate a substrate 28 under inspection being imaged,i.e., sampled, nine times at a constant rate by a receiver 58, such as aline camera. Each FIG. 1A-1I illustrates a single image position, i.e.,the location on the substrate where the images 32A-I are acquired withrespect to the center of the frog-leg robot 113. FIG. 1J illustrates theimages 32A-I, or “image slices” of the substrate 28, as lines across thesubstrate surface. To detect micron size particles and aberrations onthe surface of the substrate, each of the images 32A-I is typicallynarrow, less than 1 mm. For clarity, FIGS. 1A-1J represent only afraction of the number of image positions required to completely imagethe substrate 28. As illustrated by FIG. 1J, the distance between eachimage 32A-I is variable.

FIG. 2 is a graph of the non-uniform distance imaging of the substrate28 of FIG. 1 with respect to time. The y-axis represents the distance Yfrom the substrate center 52 to the frog-leg robot center 45. Further,the y-axis represents delta-Y, the distance between the image positionsA-I. The x-axis represents the time from first image position A to thelast image position 1. The velocity curve 205 illustrates the velocitychange dv/dt (i.e., acceleration) of the blade center 52 during theimaging process due to the acceleration and deceleration of thesubstrate transport system. Additionally, curve 205 illustrates thevelocity change between A and image position B is greater than thevelocity change dv/dt between image positions H and I. The changingsubstrate velocity with respect to time results in a variation indelta-Y between the image positions.

FIG. 3 is an illustration of a distorted substrate output image 30 on adisplay 300 due to the non-linear imaging process illustrated by FIGS. 1and 2. Generally, the display 300 is a linear device such as a monitor,television, and the like, where the screen is refreshed at a constantrate and requires a linear input to properly display an image. Thex-axis and y-axis of the display 300 represent the distance from thecenter of the image, e.g., the substrate 28. The display 300 may be usedto determine a coordinate of a particle and/or a defect on the substratesurface. For example, a particle at the center of the substrate 28 is0,0. However, as the inspection system is acquiring the images at aconstant rate from a non-linear system, the defect coordinate isinaccurate relative to the actual position on the substrate surface. Forexample, for an eight-inch diameter substrate 28 displayed on thedisplay 300, the first image 32A is positioned at approximately minusfour inches from the center of the substrate 28. Subsequent images 32B-Iare displayed with a spacing of about 1 inch between each image.However, the actual spacing between the images are not uniform asindicated by FIGS. 1J and 2. For example, the delta-Y between imageposition A and B is about 2 inches. Therefore, as the acquired images32A-I from the inspection system are displayed on the display 300, theactual distance between the images 32A-I changes relative to theconstant refresh rate of the display 300, distorting the substrate image30. Thus, the distorted image 30 causes inaccurate coordinatemeasurements of the substrate surface.

FIGS. 4A-G illustrate an in-situ inspection system where the receiver 58is a time-domain integration (TDI) camera. The TDI camera may be used toincrease the sensitivity for imaging moving substrates. The TDI cameraoperates in a similar way to other cameras, such as the line camera,except the TDI camera operates on the principle of integrating multipleexposures, i.e., multiple images, of the same subject, to increase theoverall exposure of the subject. Typically, the TDI camera has severaladjacent rows of light gathering sensors that image the same subject, asthe subject passes beneath each sensor row. For example, FIG. 4Cillustrates one TDI camera having four rows of sensors A-D representing4096 bytes of information per row.

FIG. 4D illustrates an imaging sequence of a desired image position Hcorresponding to image 32H. The image sequence is set to an integrationtime T between each exposure. At the start of the sequence, sensor row Ais given an image trigger signal by, for example, a controller, or user,and acquires the first image of image position H and sends the imagedata of image H to sensor set row B. At the end of the integration timeT a second image of image position H is taken by sensor row B and isintegrated with the previous image position H from sensor row A, and soon for each sensor row C and D. Unfortunately, to ensure that eachsensor row (e.g., A-D) is identically aligned with the image position H,the conventional TDI camera typically requires that the moving substratebe synchronized with the integration time T and linear in movement.However, if the substrate image position H is not synchronized andaligned for each sensor row A-D, the resultant image is a composite ofdifferent images resulting in a defective and perhaps meaninglesscomposite image output. For example, as illustrated by FIG. 4D, imageposition H is not aligned with each of the sensors A-D which may resultin a distorted composite (i.e., integrated) image.

Therefore, there is a need for a method and apparatus for in-situinspection and imaging of substrates in non-linear systems that provideaccurate image results.

SUMMARY OF THE INVENTION

Aspects of the invention generally provide a method and apparatus forsubstrate inspection and imaging. One embodiment of the inventionprovides an apparatus including at least one transmitter, at least onereceiver, a controller coupled to the receiver and the transmitter wherethe controller includes a processor and at least one substrate imagingprogram that when executed on the processor performs the steps ofdetermining the trigger intervals for at least two trigger signals forthe acquisition of at least two images on a substrate surface movingwith non-linear motion where a first trigger interval corresponds to afirst image position and a second trigger interval corresponds to asecond image position, then transmitting one or more optical signalsfrom the transmitter to the first and second image positions on thesubstrate surface receiving the at least two trigger signals at thereceiver where the two trigger signals include a first trigger signalcorresponding to the first trigger interval, and a second trigger signalcorresponding to the second trigger interval, and then receiving aportion of the one or more optical signals at the receiver from thefirst image position and the second image position.

In another embodiment, the invention provides for a method of substrateimaging including determining the trigger intervals for at least twotrigger signals for the acquisition of at least two images on asubstrate surface moving with non-linear motion wherein a first triggerinterval corresponds to a first image position and a second triggerinterval corresponds to a second image position, then transmittingoptical signals from a transmitter to the first and second imagepositions on the substrate surface, receiving the at least two triggersignals at a receiver where the two trigger signals include a firsttrigger signal corresponding to the first image position, and a secondtrigger signal corresponding to the second image position, thenreceiving a portion of the optical signals at the receiver from thefirst image position and the second image position; processing theoptical signals into an image, and then displaying the image.

In another embodiment, the invention provides a method of substrateimaging, including determining an interval corresponding to at least oneimage position defining an image on a non-linearly moving substratesurface, transmitting optical signals from a transmitter to the imageposition, then receiving, at a first sensor of the time-domain camera, aportion of the optical signals from the image position, processing theoptical signals into a first image, determining an integration intervalfor a second sensor of the time-domain camera corresponding to thenon-linear movement of the substrate surface, then receiving, at thesecond sensor, the optical signals from the image position, processingthe optical signals into a second image, and then integrating the firstand second images.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the invention are attained and can be understood in detail, amore particular description of the invention, briefly summarized above,may be had by reference to the embodiments thereof which are illustratedin the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIGS. 1A-1I illustrate a substrate surface being imaged nine times by aprior art optical inspection system.

FIG. 2 is a graph and illustration of prior art non-linear motionimaging.

FIG. 3 is an illustration of an output image as a result of the imagingprocess illustrated by FIGS. 1 and 2.

FIGS. 4A-D illustrates a time-domain integration camera and an imagingsequence during non-linear substrate movement.

FIG. 5 is plan-view of a cluster tool that may be used to advantage.

FIG. 6 is a diagram illustrating a frog-leg robot.

FIGS. 7-9 are cross-sectional views illustrating an imaging system andsubstrate motion within a chamber.

FIG. 10 depicts a process control system in which embodiments of theinvention may be implemented.

FIG. 11 is a flow diagram for a method for an imaging system that may beused with the invention.

FIGS. 12A-12H illustrate a substrate being imaged eight times by animaging system using the method of FIG. 12.

FIG. 13 is a graph and illustration of a non-linear motion imaging.

FIG. 14 is an illustration of an output image as a result of the imagingprocess of FIGS. 11-13.

FIG. 15 is a diagram illustrating a time domain integration cameraimaging a position on a substrate surface during non-linear motion usingthe method of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention have particular advantages in multi-chamberprocessing systems. One exemplary multi-chamber processing systemcommonly used in the semiconductor industry, well suited for supportingthe imaging apparatus and method described herein, is known as a clustertool. A cluster tool is a modular system comprising multiple chambersthat perform various functions including substrate center-finding andorientation, degassing, annealing, deposition and/or etching. Themultiple chambers are mounted to a central transfer chamber which housesa robot adapted to shuttle substrates 28 between the chambers. Thetransfer chamber is typically maintained at a vacuum condition andprovides an intermediate stage for shuttling substrates 28 from onechamber to another and/or to a load lock chamber positioned at a frontend of the cluster tool.

FIG. 5 is a plan view of one embodiment of a processing system 100 inwhich embodiments of the invention may be used to advantage. Thearrangement and combination of chambers may be altered for purposes ofperforming specific steps of a fabrication process. The processingsystem 100 generally includes a plurality of chambers and robots and ispreferably equipped with a processing system controller 102 programmedto carry out the various processing and inspection methods performed inthe processing system 100. A front-end environment 104 is shownpositioned in communication with a pair of load lock chambers 106. Atleast one pod loader 108 is disposed in the front-end environment 104 iscapable of linear, rotational, and vertical movement to shuttlesubstrates 28 between the load locks 106 and a plurality of pods 105which are mounted on the front-end environment 104. The load locks 106provide a first vacuum interface between the front-end environment 104and a transfer chamber 110. Two load locks 106 are provided to increasethroughput by alternatively communicating with the transfer chamber 110and the front-end environment 104. Thus, while one load lock 106communicates with the transfer chamber 110, a second load lock 106communicates with the front-end environment 104. A robot 113 such as,for example, a frog-leg or polar type is centrally disposed in thetransfer chamber 110 to transfer substrates 28 from the load locks 106to one of the various processing chambers 114 and pre/post processingchambers 116. The processing chambers 114 may perform any number ofprocesses such as physical vapor deposition, chemical vapor deposition,and etching while the pre/post processing chambers 116 are adapted fordegassing, orientation, cool down and the like. The processing systemcontroller 102 is electrically coupled to at least one imaging system150 by an I/O (input-output) cable 90. In one aspect, the processingsystem controller 102 is adapted to provide command signals to, andreceive data from, the imaging system 150.

FIG. 6 illustrates one embodiment of the invention modeling the frog-legrobot 113. The robot 113 comprises a body 134 and an upper robot arm111A and lower robot arm 111B rotatably coupled on one end to the robotbody 134. Each robot arm 111A-B comprises an arm member 115 having alength A, and an arm extensions 117 having a length B. The armextensions 117 are rotatably coupled on a second end 122 of the armextensions 117 to a pivot point 132 of the blade 48. The distancebetween the robot center 45 and the blade center 52 is Y. The distancedfrom the pivot point 132 to the blade center 52 is D. The offset heightof the pivot points 132 relative to the robot center 45 and blade center48 is C. As the stepper motor 133 rotates step-wise, each of the armmembers 115 and extensions 117 are rotated with respect to θr. The rangeof values for θr is about zero degrees to about 90 degrees relative to ahorizontal line connecting the robot center 45 and the blade center 52.

Referring to FIG. 6, the retraction and extension distance Y of therobot blade center 52 relative to the center of the robot 45 isrepresented by the following equationY=D+A Cos θr+√{square root over (B²−(A Sin θr−C)²)}  (1)Where θr is represented by the following equation $\begin{matrix}{{\theta\quad r} = {{{Tan}^{- 1}\left( \frac{C}{Y - D} \right)} + {{Cos}^{- 1}\left( \frac{A^{2} + C^{2} + \left( {Y - D} \right)^{2} - B^{2}}{2A\sqrt{C^{2} + \left( {Y - D} \right)^{2}}} \right)}}} & (2)\end{matrix}$

The range of θr from about zero degrees to about 90 degrees correspondsto a minimum distance and maximum distance for Y, respectfully. Forexample, when the arm members 115 and the extensions 117 are fullyextended and where C is about zero, θr is about zero degrees and Y isabout the length of A plus B and D. When the arm members 115 and theextensions 117 are fully retracted, θr is about ninety degrees and Y isequal to about D.

FIGS. 7-9 illustrate one embodiment of an in situ imaging system 150mounted to the pre/post processing chamber 116 and the movement of asubstrate 28 into the pre/post processing chamber 116. The pre/postprocessing chamber 116 generally includes a chamber body havingsidewalls 118 and a bottom 104. A support member 106 may be disposedthrough the bottom of the pre/post processing chamber 116 to receive andsupport a substrate 28 introduced into the pre/post processing chamber116. The support member 106 may include a cooling system, such as fluidchannels and cooling fluid source, to provide substrate cooling.

A lid assembly 700 having the imaging system 150 mounted thereon isdisposed at the upper surface of the chamber walls 118 and forms a sealtherewith. The lid assembly 700 generally includes a body defining aport 710 therein to provide an aperture for a receiver unit 58, such asa charge coupled device (CCD), line camera, and the like, for receivingoptical inputs from within the pre/post processing chamber 116. Inaddition, the lid assembly 700 generally includes a port 712 therein toprovide an aperture for a light source 56 for illuminating the substrate28. The receiver 58 and a light source 56 are secured to the lidassembly 700 by a mounting bracket 752 that may be mounted to the lidassembly 700 using conventional fasteners such as screws, bolts, and thelike. In one embodiment, the light source 56 can be a halogen lightsource, broadband light source, narrowband light source, or other lightsource capable of operating in the 400 nm to 750 nm range {Range?}. Theports 710 and 712 have energy transparent windows 722 and 724,respectively, disposed therein to provide vacuum isolation within thepre/post processing chamber 116 on which the lid assembly 700 isdisposed. The lid assembly 700 also includes an optics assembly 721disposed between the window 724 and the light source 56. The opticsassembly 721 can include any combination of filters, diffusers, lenses,and the like adapted to modify the light being emitted from the lightsource 56. The port 710 is disposed at an angle 0 relative to ahorizontal line in which the substrate 28 would be introduced into thepre/post processing chamber 116 (i.e., a substrate transfer path). Theangle 0 enables the receiver 58 to have a line of sight view to thesubstrate 28 as the substrate 28 enters and exits the pre/postprocessing chamber 116 on a robot blade 48. The port 712 is disposed atan angle θt relative to a horizontal line in which the substrate 28would be introduced into the pre/post processing chamber 116 and ispositioned in any desired angle suitable for the operation of thetransmitter 56.

In some embodiments, the orientation of the receiver 58 and the lightsource 56 may be automatically adjusted (as opposed to manually). Forexample, although not shown, servos or similar actuators coupled to acontrol system may be used to move the various components adjustaperture size and focus from a remote location. The ports 710 and 712may also include optical filters 761 and 762 respectively, such aspolarizers, color spectrum filters, and other bandwidth selectivemediums to attenuate, select, and filter the light spectrum. The opticalfilters 761 and 762 may be positioned on the atmospheric side of thewindows 722 and 724, or formed integrally as part of the windows 722 and724.

In one aspect, during substrate inspection the substrate surface isimaged, i.e., sampled, during the movement of the substrate 28 by theimaging system 150. For example, FIG. 7 illustrates the substrate 28 inposition for the imaging system 150 to capture the image 32A at imageposition A. FIG. 9 illustrates the substrate 28 in position for theimaging system 150 to capture an image 32G at image position G. FIG. 9illustrates the substrate 28 in position for the imaging system 150 tocapture the image 321 at image position 1.

Substrate Imaging

FIG. 10 depicts one embodiment of the processing system controller 102in which the invention may be implemented to advantage. In general, theprocessing system controller 102 includes a central processing unit(CPU) 1005 connected via a bus 1075 to a memory 1007, storage device1055, input device 1060, output device 1065, and counter/timer 1050. Theinput device 1060 can be any device to give input to the processingsystem controller 102. For example, a keyboard, keypad, light-pen,touch-screen, track-ball, or speech recognition unit could be used. Theoutput device 1065 is preferably any hardware adapted to interface andcontrol the receiver 58. The counter/timer 1050 may be any digitaldevice adapted to count up/or down in response to a specified countcommand from CPU 1005 and/or measure time. The clock 1045 sets theprocessing system controller clock rate, and may be integral toprocessing system controller 102 or be an external clock source.

Memory 1007 contains an imaging control program 1010 that, when executedon CPU 1005, provides support for controlling the imaging system 150.The imaging control program 1010 in the memory 1007 is in the form ofprogram code conforming to any one of a number of different programminglanguages. For example, the program code can be written in C, C++,BASIC, Pascal, or a number of other languages.

In one aspect, each image on the substrate 28 is given an associatedimage position corresponding to the distance Y for each image positionon the substrate surface relative to the robot center 45. For example,with reference to FIG. 3, the distance Y for image A from FIG. 1 isabout 16.8 inches, whereas the distance Y for image B is about 18.8inches, and so on for each image 32A-I. The image positions are storedin the position data structure 1015. In another aspect, each imageposition on the substrate 28 is given an associated trigger time valueas the time to acquire each image relative to a starting time. Thetrigger time values are stored in the time data structure 1035.

Memory 1007 also includes exposure data 1025 for the receiver 58 to setthe proper exposure, image capture sequence data 1030 to set thesequence the images will be acquired, time data structure 1035 which isthe duration of time between each image capture, and initialization data1015 including motor acceleration/deceleration data, calibration data,and the like. In another embodiment, the memory 1007 includesintegration process time 1040 to facilitate the control and timing ofthe integration data between each TDI image sensor row.

The memory 1007 may be random access memory sufficiently large to holdthe necessary programming and data structures of the invention. Whilememory 1007 is shown as a single entity, it should be understood thatmemory 1007 may in fact comprise a plurality of modules, and that memory1007 may exist at multiple levels, from high speed registers and cachesto lower speed but larger DRAM chips.

The storage device 1055 is preferably a direct access storage device(DASD), although it is shown as a single unit, it could be a combinationof fixed and/or removable storage devices, such as fixed disc drives,floppy disc drives, tape drives, removable memory cards, or opticalstorage. Memory 1007 and storage device 1055 could be part of onevirtual address space spanning multiple primary and secondary storagedevices.

FIG. 11 illustrates one embodiment of a method 1100 for synchronous orasynchronous control of the imaging system 150 by the processing systemcontroller 102 using, for example, the imaging control program 1010. Asnecessary, FIGS. 1-10 are referenced in the following discussion of FIG.11. In one aspect, for synchronous imaging, the processing systemcontroller 102 calculates the number of stepper motor steps tosynchronize the desired image position to the receiver 58 to accuratelyacquire each image. In another aspect, for asynchronous imaging, theprocessing system controller 102 estimates the imaging trigger time forthe receiver 58 to accurately acquire each image at each image position.

The method of FIG. 11 is entered into at step 1105, when for example theprocessing system controller 102 begins the inspection of a substrate28. Method 1100 at step 1110 gets an event such as a start-imagingtrigger signal from the processing system controller 102. Although insome embodiments the start-imaging trigger signal is established andcoordinated with the motor start sequence, other start-imaging triggersignals may be used such as light-beam, magnetic, and proximity sensors,and the like. Additionally, in some embodiments the start-imagingtrigger signal be in electrical form such as TTL, CMOS, and the like,other types of start-imaging trigger signals are contemplated includingsignals such as optical, mechanical, magnetic, and the like, adapted totrigger and control the imaging system 150.

Method 1100 at step 1115 determines whether a start-imaging triggerevent has occurred to begin the imaging process of the substrate 28. Ifthe event is not a start-imaging trigger signal, then method 1100proceeds to 1117. At step 1117, the method 1100 determines if the eventis an end-imaging event. If the event is not an end-imaging event, themethod 1100 returns to 1110 to get the next event. If the event is anend-imaging event, the method 1100 proceeds to 1150 and exits. If theevent is a start-imaging trigger event, the method 1100 proceeds to step1120 to determine the image positions of the substrate 28 usingequations 1 and 2 for each image distance Y and, for synchronous and/orasynchronous operation.

In one aspect, to calculate the image position Y for each image, thenumber of images is determined for the diameter of the substrate 28using the image width, i.e., image slice. Ideally, to accurately imagethe substrate 28, each image should abut the next image without overlapor separation. Thus, ideally, for a fixed width image, imaging insequential order, the distance delta-Y to move from the center of oneimage position to the center of the next image position is aboutequivalent to the image width. Additionally, the image width establishesthe number of images required to completely image the substrate surface.For example, for a substrate that is 300 mm in diameter having an imagesystem 150 imaging width of 1 mm would require about three hundredadjacent images. The image length generally is set to the widest portionof the substrate 28.

For synchronous operation, using the equations 1 and 2 at step 1120 themethod 1100 calculates the number of steps to reach θr for each imageposition Y, and stores them into position data structure 1020. In oneaspect, θr is a function of binary (e.g., a byte) input to the steppermotor 133 from the processing system controller 102. The binary inputsets the number of stepper motor steps, i.e. the amount of stepwiserotation, to achieve the θr.

At step 1125, the method establishes the image sequence. The imagesequence may be established in a sequential order from the first imageto the last image, e.g., image one to image three hundred, however,other sequences are contemplated. The sequence is then stored in thesequence data structure 1030.

At step 1130, method 1100 determines and sets the exposure time for eachimage position to properly expose the substrate surface. In one aspect,to determine the exposure time method 1100 determines the shutter and/orframe rate required for the desired exposure for each image position.The exposure time may be set to allow the smallest particles oraberrations of interest to be detected. However, other exposure timesare contemplated. At step 1135, the system counter/timer 1050 isinitialized. The counter/timer 1050 is used to count the number of stepsto the image positions.

At step 1140, the imaging system 150 images the substrate 28. Thesubstrate 28 may be imaged in any direction moving into or out of thepre/post processing chamber 116. For example, with reference to FIGS.7-9, the robot 113 begins to move the substrate 28 on the blade 48 intothe pre/post processing chamber 116 as the stepper motor 133 isinitiated by processing system controller 102.

In one aspect, during the imaging sequence, the counter/timer 1050 isstarted about simultaneously with the stepper motor 133 and counts thenumber of stepper motor steps to reach each image position using theposition data from position data structure 1020. For example, when thenumber of stepper motor steps equals the number of steps stored in theposition data structure 1020 representing the first image position, theimaging system 150 acquires the first image. Upon completion of theacquisition of the first image, the counter/timer 1050 continues tocount the number of steps corresponding to the second image position.When the number of counts equals the number of steps stored in theposition data structure 1020 representing the second image position, theimaging system 150 acquires the second image, and so on for each image.The method 1100 at step 1145 determines if the last image position hasbeen reached, i.e., the end of the sequence data 1030, if so then themethod 1100 returns to step 1110 to wait for the next event. If not,then the method 1100 returns to step 1140.

For asynchronous operation, at step 1120, the method 1100 determines thetrigger time for each image relative to a start trigger. Generally, thestart trigger is set to about zero with reference to the start of theimaging sequence but may be any time value leading or lagging the imagesequence. To determine the trigger time, method 1100 obtains the steptimes, i.e., step time and dwell times at each step, from the steppermotor response curve data located within the initialization data 1015 ofmemory 1007, and the number of stepper motor steps using equations 1 and2 for each image position, then sums the number of step times to obtainthe specified trigger time for each image position. The results of thetrigger times are then stored within the time data structure 1035.

At step 1130, method 1100 determines and sets the exposure time for eachimage. In one aspect, to determine the exposure time method 1100determines the shutter and/or frame rate required for the desiredexposure for each target. The exposure time may be set to allow thesmallest particles or aberrations of interest to be detected. However,other exposure times are contemplated. At step 1135, the clock 1145 isstarted counting the time to the first image position. The imagingsystem 150 begins acquiring the image at the specified trigger timeintervals with respect to the start trigger received at step 1115.

At step 1140, the imaging system 150 acquires images of the substrate28. The substrate 28 may be imaged in any direction moving into or outof the pre/post processing chamber 116. For example, with reference toFIGS. 7-9, the robot 113 begins to move the substrate 28 on the blade 48into the pre/post processing chamber 116 as the stepper motor 133 isinitiated by processing system controller 102.

In one aspect, the counter/timer 1050 is started about simultaneouslywith the stepper motor and counts the time to reach the image positionsusing the trigger time data from time data structure 1035. For example,when the trigger time equals the trigger time stored in the time datastructure 1035 representing the first image position, the imaging system150 acquires the first image. Upon completion of the acquisition of thefirst image, the counter/timer 1050 continues to count the timecorresponding to the second image position. When the trigger time equalsthe trigger time stored in the time data structure 1035 representing thesecond image position, the imaging system 150 acquires the second image,and so on for each image. The method 1100 at step 1145 determines if thelast trigger time has been reached, i.e., the end of the sequence data1030, if so then the method 1100 returns to step 1110 to wait for thenext event. If not, then the method 1100 returns to step 1140.

FIGS. 12A-H illustrate a substrate 28 being imaged eight times at avariable rate by the imaging system 150 comprising a receiver 58, usingmethod 1100. The variable rate corresponds to the non-linear movement ofthe substrate 28. Each FIG. 12A-12H illustrates a single image positionA-H, i.e., the location on the substrate where images 62A-H areacquired. FIG. 12J illustrates the images 62A-H, or “image slices” ofthe substrate surface as lines across the substrate surface. To detectmicron size particles and aberrations on the substrate surface, each ofthe images 62A-H is typical very narrow, less than 1 mm, so a largenumber of images are required to completely capture the substrate image.For clarity, FIGS. 12A-J represent only a fraction of the number ofimage positions A-H required by the imaging system 150 to fully capturethe substrate image. As illustrated by FIG. 12J, the distance (i.e.,delta-y) between each image positions is about identical.

FIG. 13 is a graph of the non-uniform time imaging of the substrate 28of FIG. 1 with respect to distance using method 1100. The y-axisrepresents the distance Y from the substrate center 52 to the frog-legrobot center 45. Further, the y-axis represents the delta-Y, thedistance between the image positions A-H. The x-axis represents the timefrom first image position A to the last image position H. The velocitycurve 1305 illustrates the velocity change dv/dt (i.e., acceleration) ofthe blade center 52 during the imaging process due to the accelerationand deceleration of the substrate transport system. Additionally, curve1305 illustrates the velocity change between A and image position B isgreater than the velocity change dv/dt between image positions G and H.The variable image trigger time for each image position A-H compensatesfor the changing system velocity resulting in about a constant delta-Ybetween each image position A-H.

FIG. 14 is a diagram of an image output using method 1100 for eithersynchronous or asynchronous operation. The x-axis and y-axis representthe distance from the center of the displayed substrate 28.

Generally, the display 300 is a linear device such as a monitor,television, and the like, where the screen is refreshed at a constantrate and requires a linear input to properly display an image. Thex-axis and y-axis of display 300 represent the distance from the centerof the substrate 28. Using method 1100, the imaging system 150 isacquiring the images at a non-linear rate corresponding to thenon-linear system therefore a surface coordinate is about accurate. Forexample, for an eight-inch diameter substrate the first image 61A iscorrectly positioned at minus three and one-half inches from the centerof the substrate, as it is the first image on the display 300. As therate of imaging is variable and is an function of time, or steps, toreach the correct image position, subsequent images 61A-H are spacedabout the same apart, resulting in a linear non-distorted image ofsubstrate 28.

As the coordinate positions on the display 300 are about accurate to theactual substrate surface, the displayed image 60 may be used to locate aparticle and/or defect on the substrate surface. A particle at thecenter of the substrate 28 is 0,0. For example, A particle at 1,0.5would indicate that, measured from the center of the image 60, theparticle would be 1 inch along the x axis and 0.5 inches along the yaxis from the center of the substrate 28. Thus, as the image correlatesto the actual substrate surface dimensions the image coordinate x,y fora particle or aberration should match the actual location of the partialor aberration on the substrate surface.

FIG. 15 illustrates one embodiment of the imaging system 150 where thereceiver 58 is a TDI camera adapted to receive signals from theprocessing system controller 102 to trigger each multiple exposure tothe number of steps between each TDI sensor row A-D for synchronousoperation, or vary the image process time T for asynchronous operation.

The TDI camera has several rows of light gathering sensors A-D thatacquire the same image position as the image position passes beneatheach sensor row. As each row of the TDI camera is exposed, acquiring theimage, the image data is then passed to the next row and subsequentlyadded, i.e., integrated, with the exposure of the next row of the sameimage. The variable integration process times T1-3 are the times betweeneach subsequent exposure. For example, FIG. 15 illustrates oneembodiment of the TDI camera having four rows of sensors A-Drepresenting 4096 bytes of information per row. FIG. 15 illustrates animaging sequence for multiple exposures of image position Hcorresponding to image 62H, on the substrate surface.

For synchronous operation, at step 1125, using equations 1 and 2 themethod 1100 determines the number of stepper motor steps, i.e., stepwiserotation, between each sensor row A-D where the image position H isabout properly aligned. Method 1100 stores the steps for rows A-D intothe position data structure 1020. At step 1130, the exposure is set bythe amount of time required by the sensor rows A-D to properly exposethe image position H for each sensor row A-D to acquire the image 62H.

At step 1140, the imaging system 150 images the substrate 28. During theimaging process, the counter/timer 1050 is started about simultaneouslywith the first image exposure of image position H at row A, and countsthe number of stepper motor steps to reach each subsequent imageexposure row B-D using the position data from position data structure1020. For example, when the number of stepper motor steps equals thenumber of steps stored in the position data 1020 representing the pointwhere the image position H is properly aligned with the row B forimaging, the imaging system 150 acquires the second exposure of imageposition H using sensor row B. Upon completion of the acquisition of thesecond exposure, the counter/timer 1050 continues to count the number ofsteps corresponding to the next sensor row C. When the number of countsequals the number of steps stored in the position data 1020 representingthe point where the image H is aligned with the row C for imaging, theimaging system 150 acquires the third exposure of image position H. Uponcompletion of the acquisition of the third exposure of image position H,the counter/timer 1050 continues to count the number of stepscorresponding to the last sensor row D. When the number of counts aboutequals the number of steps stored in the position data 1020 representingthe point where the image H is properly aligned with the row D forimaging, the imaging system 150 acquires the fourth exposure of imageposition H. The method 1100 at step 1145 determines if the last imageposition has been reached, i.e., the end of the sequence data 1130, ifso then the method 1100 returns to step 1110 to wait for the next event.If not, then the method 1100 returns to step 1140 to image the nextimage position.

For asynchronous operation, the integration process times T1-T3 arevaried to establish the time for image position H to be properly alignedwith each sensor row A-D. Method 1100, at step 1120 determines theintegration process time for each image position relative to the firstimage position from sensor row A. To determine integration process timesT1-T3, method 1100 obtains the step times such as step and dwell timesfrom the stepper motor response curve data located within theinitialization data 1015 of memory 1107, calculates the steps betweeneach sensor row A-B using equations 1 and 2, and counts the time betweensensor rows A-D using counter/timer 1050. Method 1100 then sums thenumber of step times between each row to obtain the specifiedintegration process times T1-T3 between each sensor row A-D. The resultsof the integration process times are then stored within the time datastructure 1035.

At step 1130, the exposure is set by the amount of integration processtime T1-T3 required by the sensor rows A-D to properly expose the imageposition H. At step 1135, the clock 1045 is started, triggering theimaging system 150. The imaging system 150 begins acquiring the image atthe specified trigger time intervals with respect to the start triggerreceived at step 1115.

At step 1140, the imaging system 150 acquires images of the substrate28. In one aspect, the counter/timer 1050 is started aboutsimultaneously with the first sensor row A image acquisition, and countsthe integration process time T1 from time data structure 1035 to reachthe second sensor row B. For example, when the counted integrationprocess time corresponds to about T1 stored in the time data structure1040, the imaging system 150 acquires the second exposure of imageposition H using sensor row B. Upon completion of the acquisition of thesecond exposure, the counter/timer 1050 continues to count theintegration process time T2 corresponding to the next sensor row C. Whenthe counted integration process time corresponds to about T2 stored inthe position data 1020, the imaging system 150 acquires the thirdexposure of image position H. Upon completion of the acquisition of thethird exposure of the image position H, the counter/timer 1050 continuesto count the integration process time corresponding to the last storedintegration process time T3 for sensor row D. When the integrationprocess time corresponds to about T3 stored in the position data 1020,the imaging system 150 acquires the fourth exposure of image position H.The method 1100 at step 1145 determines if the last image position hasbeen reached, i.e., the end of the sequence data 1030, if so then themethod 1100 returns to step 1110 to wait for the next event. If not,then the method 1100 returns to step 1140 to image the next imageposition.

It should be noted that, although embodiments of the inventionfacilitate in situ inspection and imaging of substrates while movingnon-linearly with respect to the motion of a stepper motor driven robotother embodiments are contemplated. For example, the robot may be drivenby a linear or non-linear motor having a rotational feedback mechanismto establish and monitor the desired rotational amount of the motor toadjust the position of the substrate during processing.

The foregoing embodiments provide a detection apparatus and methodcapable of linearly monitoring substrates in situ to a non-linearprocessing system. In situ inspection minimizes the need forconventional stand-alone inspection platforms comprising dedicatedactuating mechanisms such as are routinely used in the art. Further,embodiments of the invention also use to advantage components typicallyincluded in any conventional processing system, such as the robot 113.In any case, process monitoring can be performed at various positions ina processing system during normal and necessary operation sequenceswithout transferring the substrates to a separate stand-alone inspectionplatform, thereby minimizing the impact on throughput. Consequently,each substrate moving through the process system can be inspected,thereby achieving an improvement over prior art systems and processeswherein only periodic sampling was possible due to the negative effecton throughput.

While foregoing is directed to the preferred embodiment of theinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A processing system, comprising: a vacuum transfer chamber; a vacuumprocess chamber coupled to the transfer chamber; a robot disposed in thetransfer chamber and configured to transfer a substrate between thetransfer chamber and the process chamber; a sensor positioned to acquireof images of a substrate surface while being moved by the robot; and acontroller coupled to the sensor, wherein the controller comprises aprocessor and at least one substrate imaging program containinginstructions, that when executed on the processor, causes the processingsystem to perform a method comprising: acquiring, via the sensor, afirst image of the substrate while being transported in a firstdirection at a first velocity by the robot; and acquiring, via thesensor, a second image of the substrate while being transported in thefirst direction at a second velocity by the robot, wherein the first andsecond images have equal width in the first direction.
 2. The system ofclaim 1, wherein acquiring via the second image further comprises:adjusting an exposure time of the sensor between the first and secondimages.
 3. The system of claim 1, wherein the sensor further comprises:a transmitter and a receiver.
 4. The system of claim 3, wherein thetransmitter further comprises: a time-domain integration camera, a linecamera, a CCD camera, or combinations thereof.
 5. The system of claim 3,wherein the receiver further comprises: a broad band light source, anarrow band light source, a halogen light source, or combinationsthereof.
 6. The system of claim 1, wherein the instructions contained bythe at least one substrate imaging program, when executed on theprocessor, causes the processing system to perform the method furthercomprising: acquiring, via the sensor, a third image of the substratewhile being transported in the first direction by the robot, wherein adistance between the first, second and third images are equal.
 7. Thesystem of claim 6, wherein acquiring the third image further comprises:adjusting at least one of a time or distance interval between imageacquisitions.
 8. The system of claim 6, wherein acquiring the thirdimage further comprises: determining a number of motor steps required tomove the substrate between image acquisitions.
 9. The system of claim 1,wherein the instructions contained by the at least one substrate imagingprogram, when executed on the processor, causes the processing system toperform the method further comprising: acquiring via the sensor a thirdimage of the substrate while being transported in the first direction ata velocity different than at least one of the first or secondvelocities, wherein a width of the third image in the first direction isequal to the width of the first and second images.
 10. A method foracquiring images of a substrate in a vacuum processing system,comprising: acquiring, via a sensor, a first image of a substrate beingtransported in a first direction at a first velocity; and acquiring, viathe sensor, a second image of the substrate while being transported inthe first direction at a second velocity, wherein the first and secondimages have equal width in the first direction.
 11. The method of claim10, wherein acquiring via the second image further comprises: adjustingan exposure time utilized to obtain the second image.
 12. The system ofclaim 10, acquiring via the images further comprises: a transmitting abeam of energy; and reflecting the beam of energy to a receiver.
 13. Thesystem of claim 12, wherein the transmitting the beam of energy furthercomprises: generating the beam from a broad band light source, a narrowband light source, a halogen light source, or combinations thereof. 14.The system of claim 10, wherein the acquiring the first image furthercomprises: acquiring the first image using a time-domain integrationcamera, a line camera, a CCD camera, or combinations thereof.
 15. Thesystem of claim 10 further comprising: acquiring a third image of thesubstrate while being transported in the first direction, wherein adistance between the first, second and third images are equal.
 16. Thesystem of claim 15, wherein acquiring the third image further comprises:adjusting at least one of a time or distance interval between the imageacquisitions.
 17. The system of claim 15, wherein acquiring the thirdimage further comprises: determining a number of motor steps required tomove the substrate between the image acquisitions.
 18. The system ofclaim 10 further comprising: acquiring via the sensor a third image ofthe substrate while being transported in the first direction at avelocity different than at least one of the first or second velocities,wherein a width of the third image in the first direction is equal tothe width of the first and second images.
 19. A method for acquiringimages of a substrate in a vacuum processing system, comprising: movinga substrate in a first direction in a vacuum processing system; andacquiring a plurality of images of the substrate while being transportedin the first direction, wherein at least two images are obtained whilethe substrate is moving a different velocities, wherein the images haveequal width in the first direction.
 20. The method of claim 19, whereinacquiring the images further comprises: timing the acquisition of theimages such that a distance between the images are equal.
 21. The methodof claim 19, wherein acquiring the images further comprises: spacing theacquisition of the images such that a distance between the images areequal.
 22. The method of claim 21, wherein spacing the images furthercomprises: determining a number of motor steps required to move thesubstrate between the image acquisitions.
 23. The method of claim 21further comprising: analyzing the images to detect particles oraberrations on a surface of the substrate.